<!doctype html>
<html lang="en">
  <head>
    <meta charset="UTF-8">
    <title>编程练习一</title>
    <style type="text/css">
      * {
        margin: 0;
        padding: 0;
        font-size: 13px;
        list-style: none;
      }
      .menu {
        width: 210px;
        margin: 50px auto;
        border: 1px solid #ccc;
      }
      .menu p {
        height: 25px;
        line-height: 25px;
        font-weight: bold;
        background: #eee;
        border-bottom: 1px solid #ccc;
        cursor: pointer;
        padding-left: 5px;
      }
      .menu div ul {
        display: none;
      }
      .menu li {
        height: 24px;
        line-height: 24px;
        padding-left: 5px;
      }
    </style>
    <script type="text/javascript">
      window.onload = function () {
        var menu = document.getElementById('menu');
        var ps = menu.getElementsByTagName('p');
        var uls = menu.getElementsByTagName('ul');
        for (var i in ps) {
          ps[i].id = i;
          ps[i].onclick = function () {
            var u = uls[this.id];
            if (u.style.display == 'block') {
              u.style.display = 'none';
            } else {
              u.style.display = 'block';
            }
          }
        }
      }
    </script>
  </head>
  <body>
    <div class="menu" id="menu">
      <div>
        <p>Web前端</p>
        <ul style="display:block">
          <li>JavaScript</li>
          <li>DIV+CSS</li>
          <li>jQuery</li>
        </ul>
      </div>
      <div>
        <p>后台脚本</p>
        <ul>
          <li>PHP</li>
          <li>ASP.net</li>
          <li>JSP</li>
        </ul>
      </div>
      <div>
        <p>前端框架</p>
        <ul>
          <li>Extjs</li>
          <li>Esspress</li>
          <li>YUI</li>
        </ul>
      </div>
    </div>
  </body>
</html>